1. Field of the Invention
This invention relates to the use of a new class of boron hydride (borane)-containing polymeric reagents reducing agents.
2. The Prior Art
Since the 1930's, it has been recognized that hydrides of boron, such as diborane (B.sub.2 H.sub.6), are useful strong chemical reagents. As pointed out in Chapter 17 of H. C. Brown's 1962 book, Hydroboration (W. A. Benjamin, Inc.), diborane may be used to reduce aldehydes, ketones, alkyl halides, lactones, oxides, esters, acids, nitriles, and olefincally-unsaturated materials. Diborane also enters into a wide range of hydroboration reactions as are set forth in other chapters of Brown's book. Unfortunately, diborane is a gas which makes its use often inconvenient. Diborane also suffers from the disadvantage of being explosive and so reactive that it is not suitably stable for many applications. It is so unstable that is cannot be safely stored over prolonged periods and used as required in the laboratory or in industrial scale applications, but generally must instead be generated at each demand. One solution to this problem has been proposed by Braun et al at page 2388 of Volume 36 (1971) of J. Org. Chemistry. They note that diborane can be stabilized, while retaining sufficient reactivity for most hydroboration and reduction applications, by forming a dimethyl sulfide adduct, ##STR1##
This adduct is a low-boiling liquid which vaporizes readily (boiling point:35.degree.-40.degree. C), so it cannot be simply handled. This stabilized form of diborane has an additional serious drawback of its own; when it reacts and frees its complexed BH.sub.3, it also releases dimethyl sulfide gas as a coproduct. Dimethyl sulfide gas is the most obnoxious of the odiferous alkyl sulfides, and creates a major problem, not only contaminating other reactants and products, but also requiring the use of hoods or other enclosed work spaces to avoid fouling the entire area of use.
It is an object of this invention to provide a new form for boron hydride reagents which will eliminate the problems associated with the prior art and permit wider and more convenient use of boron hydride.